Believing in the inviolability of the small set of rules that they have managed themselves to acquire, they condemn others from a different dialect background, or who have not had the same educational opportunities as themselves, for not following those same rules. Enthused by the Stalinesque policing metaphor, they advocate a policy of zero tolerance, to eradicate all traces of the aberrant behaviour. This extreme attitude would be condemned by most people if it were encountered in relation to such domains as gender or race, but for some reason it is tolerated in relation to language. Welcomed, even, judging by the phenomenal sales of Eats, Shoots and Leaves.
—David Crystal, British linguist, How Language Works, January 5, 2006